The invention relates to a device for separating the components of a heterogeneous mixture and its uses.
In many industrial applications, we can be brought to separate at least two non miscible fluids, for example a gas and a liquid, two non miscible liquids or the phases of a ternary mixture made up of two liquids and a gas. Furthermore, often times the initial mixture contains solid particles we would prefer to introduce in one or the other of the separated fluids.
To perform this operation, several known procedures are used, among which are the following:
gravity separators. These are rather large devices in which the emulsion""s residence time is of several tens of seconds. The corresponding technology is known and is part of the engineer""s art. In particular, decanters equipped with internal parallel plates are used;
centrifuges. These are devices driven by a motor in which the heavy phases are centrifuged and the light phases are centripeted under the action of a rotating field of flow. The tangential velocity of the fluid in the device is proportional to the radius, which limits its efficiency.
cyclones. These are stationary devices in which the mixture is introduced around the circumference of the device tangentially to the wall farthest from the axis. This creates a flow whose tangential velocity increases as we get closer to the center of the device, or at least to the output ports. These output ports are located close to the axis of the device and the liquid passes through them following an overall axial direction. The efficiency of these devices is relatively good and they are mostly used to obtain the separation of solids and liquids, the sorting of particles based on their sizes or a liquid-liquid separation. Nevertheless, these cyclones do have certain disadvantages due to the friction of the fluid against the walls. This results in the creation of a strong internal turbulence which tends to remix the species, brake the rotation and produce significant losses of charges.
Furthermore, in a liquid-liquid separation, these traditional cyclones can only operate if their size is small, typically less than 80 mm in diameter. Therefore, it is essential they be placed side by side if we wish to have significant flows pass through. This is very limiting when we are for example trying to perform a water-oil separation at the bottom of an oil well;
the rotating separator with a longitudinal peripheral feed. This is a separator whose walls rotate around an axis like those of a centrifuge, where the separation takes place in a cylindrical chamber, and the feed of said chamber follows an axial direction through canals parallel to the rotation axis located around the circumference of the cylindrical chamber, and the separated fluid exits through cylindrical ports pierced at the extremities of the rotating chamber. Such a separator is described in the French patent number 2 592 324 filed on Jan. 2, 1986 whose inventors are Y. Lecoffre and J. Woillez. They make it possible to execute an entry in the rotating mark following an axial direction so that in the absolute mark, the fluid enters with a rotation velocity almost exactly equal to that of the cylindrical chamber. This makes it possible to strongly limit the tangential friction on the walls of the chamber. We then obtain a field of velocities in the Vortex type chamber in which the tangential velocity is inversely proportional to the radius. Therefore it increases rapidly as we get closer to the center of the device, which results in spectacularly increasing the radial migration velocities of the globules to be separated.
The device performs a very efficient separation despite the fact that the residence times are close to one second. Therefore it is particularly compact. Furthermore, and this is one of the most significant characteristics, it can operate in a wide range of flows of the entry mixture, whose ratio between the extreme flows is greater than 20. In its current versions of separation of two non miscible liquids, this separator has the following disadvantages:
the separated light liquid always contains a significant and often predominant quantity of heavy liquid;
the losses of charges on the heavy liquid are relatively significant;
the losses of charge on the light liquid are practically double the losses of charge on the heavy liquid. Thus, in certain cases, we reach losses of charge of approximately ten bars;
the device only treats mixtures that contain a small quantity of light liquid, typically in the 1 to 3% range;
the device is driven via a motor placed laterally and a belt, which strongly increases its lateral congestion and prohibits its use in pipes with small diameters, as is the case in the oil industry.
The American patent number 3 405 803 relates to a vortex separator for the clarification of a suspension that contains particles. This separator has a vortex chamber 1 with a tapered lower part, the evacuation of the clarified suspension takes place on the same side as the introduction of the suspension to be clarified. Only the heavy particles are eliminated through the extremity 3 of the vortex chamber 1 on the side opposite that of the introduction of the suspension to be clarified.
Such a separator, if it makes possible the clarification of a suspension that contains particles, does not however perform a real separation of the components of the suspension.
The application for the European patent published under number 37 347 proposes a procedure and a device for separating the particles in a fluid. The procedure requires that the suspension to be treated be introduced following a direction that is slightly oblique in relation to the longitudinal axis of the enclosure, so that is has an initial angular velocity that is greater than the angular velocity of the enclosure. The device (FIGS. 1, 5, 78, 9) consists of a tapered revolution enclosure 1 that rotates around its axis, an outlet 12, 13 of the purified suspension and the separated fractions located at the extremity opposite that of the enclosure where the inlet 8 of the suspension is located, where the outlet 12 of the heaviest fraction is located around the circumference of the enclosure, meaning that its outside diameter is equal to the inside diameter of the enclosure 1. Furthermore, this outside diameter of the outlet 12 is even often increased by an enlargement of the enclosure at the level of this outlet 12, as can be seen in FIGS. 1, 5 and 7. These arrangements prevent the development of a cyclonic effect necessary to obtain a good separation. Furthermore, the device proposed in this application for European patent calls for an auxiliary fluid, it must have large dimensions and it operates with a low average centrifugal acceleration and a long residence time.
The object of this invention is to remedy the afore-mentioned disadvantages. Therefore it relates just as well to rotary separators with a peripheral feed as it does to stationary separators provided they operate with unusual characteristics. Therefore this invention intends to answer the following needs:
limit the losses of charge:
be able to integrate the separator in pipes with small diameters and especially an oil production well pipe;
make it possible to separate the fluids contained in liquid-liquid mixtures rich in one or the other of the components;
be able to integrate the separator to a pump shaft line in the case of a rotary separator;
be able to separate solids;
reinject the separated solids in one or the other of the liquid phases;
separate gases;
perform a separation of gases, then of the liquids and the solids in an integrated device;
integrate a finish separator on one or the other of the liquids to be separated;
implement means for regulating the flows of liquid;
implement arrangements that make it possible to limit the fluctuations of concentration at the inlet of the separator;
implement arrangements that make it possible to optimize the feeding conditions of the device.
In the existing devices, the output of the less dense liquid usually takes place through pipes of small diameter sometimes located on the same side as that of the entry of the mixture, sometimes on the opposite side from the entry of the mixture. Furthermore, these devices always operate with a reduced "xgr" flow of less than 0.1. This "xgr" parameter is determined by   ξ  =      Q          π      ⁢              xe2x80x83            ⁢              R        0        2            ⁢              V        TO        2            
where Q is the flow in m3/s, Ro is the external radius in meters at the entry of the pipe in which the separation takes places and VTO is the tangential velocity in meters per second at this same point. The consequence of this conception is that the frictions in the device are very strong due to the low value of the flow coefficient. Furthermore, despite this strong friction the losses of charge are also significant because recuperation of the light liquid in done at the point where the pressure in the separator is the weakest, meaning on its axis. Lastly, a considerable quantity of heavy fluid passes through the output of the light liquid because of the recirculations that take place in the output of the heavy liquid. Therefore, we always collect a light liquid charged with heavy liquid.
We are aware of, through EP-A- 0 037 347, a device for separating the components of a heterogeneous mixture, where this device consists of a separation chamber that has at one of its extremities an inlet and at the other of its extremities an outlet that consists of a first annular orifice, coaxial to said chamber, and a second annular orifice, coaxial to said first annular orifice and whose outside diameter is less than the inside diameter of said first annular orifice, and where said separation chamber has a cylindrical shape and the outside diameter of said first annular orifice is equal to the inside diameter of said chamber.
This invention is interested in this general type of device and it is characterized by the fact that the separation chamber has a cylindrical shape, and by the fact that the outside diameter D1 of the first annular orifice is less than the inside diameter Do of the chamber and that the outlet of the separation chamber has:
a peripheral annular piece that extends from the wall of the separation chamber toward the axis of this chamber,
a piece that is essentially cylindrical,
a central piece with a circular transversal section,
where the essentially cylindrical piece is arranged between the peripheral annular
piece and the central piece, and the three pieces are coaxial to the separation chamber, in such a way that
the first annular orifice is comprised of the space between the peripheral annular piece and the piece that is essentially cylindrical, and
the second annular orifice is comprised of the space between the essentially cylindrical piece and the central piece.
The characteristics of the device as set forth in the invention lead to the aspiration of the light fluid, not at the center of the turbulent flow where the pressure is minimal, but following a larger radius for which the pressure is stronger which limits the losses of charge.
The separation chamber has a circular transversal section. It can be essentially cylindrical, but, contrary to what can be seen in the devices of the prior art, according to the invention, tapered shapes are to be avoided. Furthermore, the inlet and the outlet are axially separated which allows the separation to take place correctly between them.
Furthermore, an important characteristic as set forth in the invention is that the first annular orifice, namely the one that has the largest average diameter, must have a outside diameter that is less than the inside diameter of the separation chamber, this in order to obtain a satisfactory cyclonic effect.
The first annular orifice or outlet ring of the heavy liquid must be sized so that the heavy liquid exists the separator at any point of this ring and that there be no recirculations as is the case in the traditional cyclones.
In this presentation, by xe2x80x9cwidth of a ringxe2x80x9d we mean the difference of the diameters of the two circles that bound it.
For a ring with a given width, there is a minimum flow that makes it possible to meet these conditions. Therefore we always try to work at a flow rate that is greater than this minimum heavy liquid outlet ring charging flow. This minimum flow can be determined either by calculation or from experiences. For example, for a cyclone with rotating walls with an outside diameter D0 equal to 100 mm, rotating at 3000 tr/min, this minimum flow with a ring with an outside diameter equal to 70 mm and a width that is equal to 5 mm is in the range of 10 l/s. This minimum flow can be adjusted by a simple variation of the width of the heavy liquid outlet ring.
The inside diameter D3 of the second annular orifice or outlet ring for light liquid consists of the lower limit for which the flow is in a vortex type rotation. When we have a larger diameter, the flow in the separator is healthy and the separation is done correctly. For smaller diameters, the flow in the separator transforms itself into an area of dead liquid where the distribution of the tangential velocity is proportional to the current radius; this area is also called in solid rotation. From the point of view of the separation, this area is useless and, considering its low volume, its efficiency in the matter of separation is more or less non existent. We can say that, from a practical standpoint, a cyclone whose diameter D3 is at the most equal to half the outside diameter of the separator has performances in separation that are as good as if D3 were very small, but its losses of charge are very much less, for example two to ten times less than those of a traditional cyclone, with stationary or rotating walls. Always very important, the loss of charge of a cyclone only depends on the flow coefficient "xgr" and the ratio   δ  =                    D        0                    D        3              .  
In practice, the loss of charge varies as xcex42 when the extraction ring of heavy liquid has no recirculations. The smaller the diameter of the extraction pipe of the light liquid, the higher the loss of charge, this tendency is perfectly confirmed by the tests available in the literature.
Lastly, the quality of the separations, and, in particular, the residual rate of heavy liquid in the light liquid depend on the presence or absence of recirculations in the heavy liquid outlet. In the absence of recirculation, we can hope to extract a light product that is almost pure.
Through this presentation we understand the importance of the outlet ports on the performances of a liquid-liquid separator.
The device as set forth in the invention can therefore be used to treat a mixture that consists of two non miscible liquids with different densities that possibly contain a gas or a mixture of gas and/or solid particles.
The invention also relates to a procedure for separating the components of a heterogeneous mixture, where:
we introduce the mixture to be treated at the entrance of a device consisting of a separation chamber with at one of its extremities an inlet and at the other extremity an outlet consisting of a first annular orifice coaxial to said chamber and a second annular orifice coaxial to said first annular orifice and whose outside diameter is less than the inside diameter of said first annular orifice, where said separation chamber has a cylindrical shape and the outside diameter D1 of said first annular orifice is less than the inside diameter D0 of said chamber; whereas the outlet of the separation chamber has:
a peripheral annular piece that extends from the wall of the separation chamber toward the axis of this chamber,
a piece that is essentially cylindrical,
a central piece with a circular transversal section,
where the essentially cylindrical piece is arranged between the peripheral annular piece and the central piece and the three pieces are coaxial to the separation chamber, in such a way that
the first annular orifice is comprised of the space between the peripheral annular piece and the essentially cylindrical piece, and
the second annular orifice is comprised of the space between the essentially cylindrical piece and the central piece;
and we recuperate a heavy fraction through said first annular orifice and a light fraction through said second annular orifice.
According to a first method of execution of the invention, the inlet of the mixture into the separation chamber takes place through rotating peripheral canals of which at least the outlet is parallel to the rotation axis of the separator, where this separator also rotates.
According to a second method of execution of the invention, the inlet of the mixture into the rotating chamber in done through rotating radial canals, where the liquid was previously thrown by friction against rotating walls located outside the chamber itself.
According to a third method of execution of the invention, the inlet of the mixture is done through several orifices pierced in the wall of the separator, into the area of entry opposite the outlets, where these orifices penetrate tangentially into the separation chamber that is stationary.
According to a fourth method of execution of the invention, the separation chamber is stationary, but the mixture is injected into a feeding chamber whose diameter is greater than that of the actual separation chamber. This arrangement makes it possible to limit the velocities at the inlet of the device and the cumbersome emulsification that can result therefrom.
According to a fifth method of execution of the invention, a small quantity of gas is injected into the central part of the device, where this arrangement makes it possible to avoid the creation of turbulence between the heart of the solid rotation flow and the external healthy area. In some cases, it is not necessary to inject this additional gas and the gas that is naturally present at the inlet is sufficient. In this last case, if the gas flow is too strong it can be extracted through a pipe located at the center of the separator.
According to a sixth method of execution of the invention, the device is equipped with one or more additional peripheral outlets that make it possible to collect the particles and a certain quantity of heavy fluid and introduce this mixture into either one of the flows extracted at the center of the device.
According to a seventh method of execution of the invention, the dimensions of the outlet ports can be regulated continuously by an action on the circular separation lip of the two flows.